1. Field of the Invention
The present invention relates to a disk drive apparatus equipped with a first amplifier for amplifying a read signal read by a head from a disk medium, and a second amplifier for further amplifying the read signal amplified by the first amplifier, and more particularly to an apparatus and method for enabling a single signal line connecting the first and second amplifiers to be used for both the transmission of a read signal from the first amplifier to the second amplifier, and the transmission of a control signal from the second amplifier to the first amplifier.
2. Description of the Related Art
Hard disk drives (HDDs) are known as disk drive apparatuses for reading data recorded on disk mediums, using heads. In hard disk drives, data magnetically recorded on a magnetic disk (magnetic disk medium) is read (reproduced) by a magnetic head. As a result, a faint read signal is output from the head. This read signal is input to a head amplifier circuit in the form of an IC chip, i.e., a so-called head IC. The read signal input to the head IC is amplified by an amplifier (read amplifier) in the head IC, and then supplied to a read/write IC (read/write channel IC). The read/write IC detects and decodes data from the signal amplified by the amplifier.
In general, the head IC is mounted on an end of a flexible printed circuit board (FPC) that is in the form of a strip, the end being remote from the magnetic head and called a base portion. In this structure, the wiring (wiring pattern) between the magnetic head and head IC is inevitably long. This means that the wiring has a high inductance and capacitance. Accordingly, a faint read signal output from the magnetic head is significantly influenced by noise.
To avoid this, Japanese Patent Application KOKAI Publication No. 2001-184619, for example, has proposed a structure in which the head IC is mounted on the suspension that supports the magnetic head. In this structure, the wiring between the magnetic head and head IC can be shortened, and accordingly the inductance and capacitance of the wiring can be reduced. However, the mounting of the head IC on the suspension is not easy in light of the present head IC size.
Consequently, a method could be devised where a first amplifier for amplifying a faint read signal output from the magnetic head, and a second amplifier for further amplifying the read signal amplified by the first amplifier are used instead of the amplifier incorporated in the head IC, the first amplifier being separate from the head IC. In this new structure, the first amplifier can have a small size and hence can be mounted on a small area near the magnetic head, e.g. on the suspension or on a stationary portion of a carriage. Moreover, since a faint read signal read by the magnetic head is first amplified by the first amplifier near the head, and is then transmitted to the second amplifier, it is less influenced by noise, even if the wiring between the first and second amplifiers is relatively long.
In the prior structure, the control signal is transmitted to the amplifier in the head IC to control the head IC. When the above-described new structure is employed, it is necessary to transmit the control signal from the second amplifier to the first amplifier. In this case, if a signal line dedicated to transmission of the control signal is employed, the number of required signal lines is increased to thereby make the layout of the new structure complicated. To avoid this, a method could be devised where the signal line used to transmit the read signal amplified by the first amplifier to the second amplifier is also used to transmit the control signal from the second amplifier to the first amplifier.
However, in the new structure in which a single signal line is used to transmit both the read signal and control signal, the read signal cannot be transmitted while the control signal is being transmitted, unlike the prior structure. Accordingly, if the control signal is transmitted while the head is reading servo data that includes position information for head positioning and is dispersedly recorded on a magnetic disk, correct position information may not be read.